In a binary PSK system, a binary signal representing data to be transmitted modulates the phase of the transmitter carrier. That is, for a first logic level, the transmitter output is a first phase, typically 0 degrees, while for a second logic level, the transmitter output is a second phase, typically 180 degrees. At the receiver, the phase of the received carrier is sensed in order to recover the data.
In prior art PSK receivers, a local reference oscillator is phase locked to the received RF signal in a phase locked loop in order to establish a local phase reference. However, the time delay required to adjust the phase and frequency of a reference oscillator in a phase locked loop can be substantial and may extend over many data bits. In certain types of communications systems, such as for example in spread spectrum communication systems, the phase synchronization time delay can be excessive, adding to the overhead needed for the operation of a data packet protocol, and in some cases, making existing protocols very difficult to implement.
Therefore, it is desirable to obtain a PSK demodulator which offers the advantage of rapidly synchronizing with the incoming signal in order to recover the originally encoded data without excessive delay.